Soil morphological, physical and chemical properties affecting Eucalyptus spp. productivity on Entisols and Ultisols

Abstract

Soil fertility in forestry systems has usually been constrained to soil nutrients, with little attention to soil morphological attributes and physical properties. Our hypothesis was that soil physical properties and morphological attributes are more closely related with commercial forest growth than soil chemical fertility. The objective of the study was to analyze the influence of soil properties, in different soil types, on dendrometric variables and productivity of clonal E. saligna and seminal E. dunnii, both widely employed in commercial plantations managed for pulp and lumber production in southern Brazil. On inventory plots with two Eucalyptus species, namely Eucalyptus saligna (clone 32864) and seminal E. dunnii, we evaluated morphological attributes and physical and chemical properties of 17 soils (Ultisols and Entisols), and the dendrometric variables tree height, tree dominant height (h100) and diameter at breast height (DBH), all measured in 7-years old plantations. Eucalyptus growth was variable and influenced by profile attributes and soil properties, but correlations between h100 and soil properties were weak (r < 0.7) and usually not significant. Tree height and DBH were not affected by Eucalyptus species, soil type and their interaction. Overall, DBH ranged from 77.98 to 304.30 mm, with an average value of 183.23 mm. By contrast, tree h100 was affected by Eucalyptus species and soil type, but not by their interaction. Trees of E. saligna (23.4 m) were taller than E. dunnii (22.1 m), while among soil types Ultisols had the tallest (23.4 m) and Entisols the shortest trees (22 m). Chemical properties were more variable in surface soil layers, whereas physical properties mainly differentiated subsurface soil layers. The lowest dominant height resulted from the interaction between the lowest field capacity and plant available water capacity and the smaller depth of Entisols' soil profile. Contrary to our hypothesis, most soil properties/attributes were not significantly correlated with dominant tree height. Neither soil physical, morphological properties nor soil chemical fertility are determinants to forest growth when these parameters are not at critical limits for forest growth, particularly with absence of extreme edaphoclimatic conditions such as low rainfall or high temperatures. Associations among soil morphological attributes, physical properties and edaphoclimatic variables should be validated in future studies to better understand their effect of forest productivity in subtropical environments.